如何在C++中使用預處理器指令的幫助下在語句之間插入語句？

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我試圖通過非常快速地打開和關閉LED來編程一個Arduino由於PWM LED矩陣。爲了控制亮度，我想在LED的開啓和關閉狀態之間添加額外的指令。亮度應該由預處理器變量設置。 Arduino擁有84MHz Cortex-M3 ARM處理器。如何在C++中使用預處理器指令的幫助下在語句之間插入語句？

這是我的代碼目前以何種方式提高亮度的簡化：

uint8_t volatile dummy = 0; 
uint8_t i; 

for (i=0;i<1<<current_layer;i++) { // every next layer has double the amount of pulses 
    LED_STATE = ON; // several pulses in one go speeds up the for loop 
    dummy = 0; // increases ON-time 
    LED_STATE = OFF; 
    LED_STATE = ON; 
    dummy = 0; 
    LED_STATE = OFF; 
    LED_STATE = ON; 
    dummy = 0; 
    LED_STATE = OFF; 
    LED_STATE = ON; 
    dummy = 0; 
    LED_STATE = OFF; 
}

現在我希望能夠根據處理器變量像這樣可以提高亮度：

#define BRIGHTNESS 2 
// inside loop 
     LED_STATE = ON; // several pulses in one go speeds up the for loop 
     #if BRIGHTNESS > 0 
     dummy = 0; // increases ON-time 
     #if BRIGHTNESS == 2 
     dummy = 0; // increases ON-time even more 
     #endif 
     #endif 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     #if BRIGHTNESS > 0 
     dummy = 0; 
     #if BRIGHTNESS == 2 
     dummy = 0; 
     #endif 
     #endif 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     #if BRIGHTNESS > 0 
     dummy = 0; 
     #if BRIGHTNESS == 2 
     dummy = 0; 
     #endif 
     #endif 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     #if BRIGHTNESS > 0 
     dummy = 0; 
     #if BRIGHTNESS == 2 
     dummy = 0; 
     #endif 
     #endif 
     LED_STATE = OFF;

由於你可以看到，這使得代碼非常難讀。我想定義一個預處理器宏，根據BRIGHTNESS的值添加這些虛擬語句。

這是代碼看起來應該像：

#define BRIGHTNESS 2 
#define B1 ... // adds dummy=0; when BRIGHTNESS > 0 or else nothing at all 
#define B2 ... 
#define B3 ... 
#define B4 ... 
// inside loop 
     LED_STATE = ON; 
     B1 B2 B3 B4 // adds a number of dummy statements based on the value of BRIGHTNESS 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     B1 B2 B3 B4 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     B1 B2 B3 B4 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     B1 B2 B3 B4 
     LED_STATE = OFF;

更妙的是插入基於可變那些語句的功能：

#define ADD_DUMMIES ... 
// inside loop 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHNESS) 
     LED_STATE = OFF;

我如何定義預處理器宏，以便他們會根據BRIGHTNESS的值插入虛假陳述？

來源

2017-08-02 uzumaki

爲什麼不使用常規的'if'語句？ – DimChtz

@DimChtz if語句如何提高可讀性？ – uzumaki

如果你打算改變LED的亮度，爲什麼它是恆定的？我錯過了什麼？ –

這是怎麼dummy = 0;語句可以與預處理器的幫助下被添加：

#define BRIGHTNESS 2 
#define _GETFOO(n) _FOO ## n 
#define ADD_DUMMIES(n) _GETFOO(n)() 

#define _FOO0() 
#define _FOO1() dummy = 0; 
#define _FOO2() dummy = 0; dummy = 0; 
#define _FOO3() dummy = 0; dummy = 0; dummy = 0; 
#define _FOO4() dummy = 0; dummy = 0; dummy = 0; dummy = 0; 

uint8_t volatile dummy = 0; 
// inside loop 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF;

編譯器插入相同的存儲指令多次其間的線條爲BRIGHTNESS使然值，只要它在邊界之內。

來源

2017-08-03 01:17:51 uzumaki

如何在C++中使用預處理器指令的幫助下在語句之間插入語句？

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